The present invention relates to a loudspeaker with a diaphragm made of pulp fibers combined with a burning resistant agent.
The diaphragms of the conventional speakers are, in general, made of pulp fibers so that there is a fear that the voice coil and the diaphragm are burnt due to overheating of the voice coil when an excessive input is applied thereto. To overcome this problem, there has been devised and demonstrated a speaker diaphragm of the type in which a burning resistance layer is formed upon the surface of the diaphragm. However, the mass of the diaphragm is increased so that the satisfactory characteristics of the loudspeaker cannot be attained. Another attempt has been made to render the diaphragm burning resistance by impregnating the pulp fibers with a water soluble inorganic burning resisting agent such as ammonium secondary phosphate. However, the diaphragm exhibits a moisture absorbing property causing the corrosion of metal parts of the speaker so that such diaphragm is not adapted for use in the speaker. There has been a further attempt for rendering the pulp fibers burning resistant by treating them with an organic agent but the treatment cost is very expensive. Furthermore much smoke is produced when the diaphragm made of such pulp fibers should be burnt.
The present invention was made to overcome the above problems.